Parse /etc/debian_version to get the full Debian version string

[eheydrick]

Describe the Enhancement

I'd love if /etc/debian_version was parsed on Debian systems. This is the only way to get the specific minor version, e.g. 10.7. Prior to Ohai 15 platform_version was read from /etc/debian_version on Debian systems but now it's read from /etc/os-release and that only contains the major version, not the minor.

Side-rant: it's unfortunate that Debian doesn't include the full version string in /etc/os-release or /etc/lsb-release like Ubuntu does.

Describe the Need

I think this would be useful for Debian users, especially those who care what minor version they are running. This could be useful for compliance reporting e.g. to prove all systems have been updated to a specific version.

Current Alternative

No good ones. If someone really wanted the minor version they could parse the version of the base-files package as it includes the minor version after the u: e.g. 10.3+deb10u7 = 10.7. Or else write something that reads /etc/debian_version but it would be nice if it was in ohai.